1. Field of the Invention
The present invention relates generally to a device and a method for sensing fluoro or halogen species, which have utility for monitoring of fluorine-containing compounds and ionic species in semiconductor process operations.
2. Description of the Related Art
In the manufacture of semiconductor devices, the deposition of silicon (Si) and silicon dioxide (SiO2), and subsequent etching, are vital operational steps that currently comprise 8-10 steps or roughly 25% of the total manufacturing process. Each deposition tool and etch tool must undergo a periodic cleaning procedure, sometimes as often as every run, in order to ensure uniform and consistent film properties.
Currently, in etching operations, etch endpoints are reached when a prescribed amount of time has elapsed. Over etch, in which the etch gas continues to flow into the reactor chamber after the cleaning etch is finished, is common and leads to longer process cycles, reduced tool lifetimes, and unnecessary global-warming-gas losses to the atmosphere (Anderson, B.; Behnke, J.; Berman, M.; Kobeissi, H.; Huling, B.; Langan, J.; Lynn, S-Y., Semiconductor International, October (1993)).
Similar issues are present in the etching of silicon nitride, tantalum oxide (Ta2O5), or silicon-based low dielectric constant materials (e.g., C- and/or F-doped SiO2).
Various analytical techniques, such as FTIR, Optical Emission Spectroscopy, and Ionized Mass Spectroscopy, can be used to monitor the etch process. However, these techniques tend to be expensive, and often require a dedicated operator due to their complexity.
It would therefore be a significant advance in the art to provide a reliable, low-cost gas sensing capability that will serve to improve the throughput and chemical efficiency of the equipment used for the deposition and etching of silicon-containing materials, including silicon, silicon nitride and silicon dioxide, by reducing and optimizing clean and etch times, and hence reducing chemical usage, lengthening equipment operating life, and decreasing equipment down time.
U.S. patent application Ser. No. 10/273,036 filed Oct. 17, 2002 for “APPARATUS AND PROCESS FOR SENSING FLUORO SPECIES IN SEMICONDUCTOR PROCESSING SYSTEMS” discloses an apparatus and method for sensing solid-state fluoro or halogen species, using a fluoro- or halogen-reactive metal filament woven around metal packaging posts or Vespel® polyimide blocks on a KF flange. Detection of the fluoro species using such metal filament-based sensors relies on monitoring the resistance changes in the metal filaments caused by their reactions with the fluorine-containing compounds. In order to ensure acceptable sensitivity and signal-to-noise ratio for such metal filament-based sensors, the dimensions and the positions of the metal filaments are controlled and optimized via uses of the metal packaging posts or the Vespel® polyimide blocks, and the absolute resistance of such metal filaments are therefore adequate for endpoint detection.
However, the Vespel® structures and/or the metal packaging posts, when used in conjunction with the metal filament sensors, may form a heat sink that reduces the signal strength of the sensor elements. Further, fabrication of the 3-dimensional sensor packages containing the metal filaments, the metal posts and/or Vespel® blocks on the KF flange is relatively labor intensive.
It would therefore be a significant advance in the art to provide a micromachined sensing device that contains a free-standing resistance sensor element that is characterized by relatively high electrical resistance, high signal strength, and low heat loss.
It will be another object of the present invention to provide a micromachined sensing device that is suitable for automated and scale-up production.
Other objects and advantages will be more fully apparent from the ensuing disclosure and appended claims.